﻿using System;
using System.Text;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
using System.Security.Cryptography;
using System.ServiceModel.Activation;

namespace Nasa8x.Web.UI
{
    [AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Required)]
    public class CaptchaService : ICaptchaService
    {
        public bool IsValidCaptcha(string captcha, string captchaHash)
        {
            return captchaHash == Convert.ToBase64String(MD5.Create().ComputeHash(Encoding.UTF8.GetBytes(captcha)));
        }

        public Message GetRandomAntiBotImage()
        {
            string captcha = generateRandomString(4).ToUpper();
            return GenerateImage(captcha, 100, 20, "Arial");
        }

        private Message GenerateImage(string text, int width, int height, string fontFamily)
        {
            Random random = new Random();

            // Create a new 32-bit bitmap image.
            Bitmap bitmap = new Bitmap(width, height, PixelFormat.Format32bppArgb);

            // Create a graphics object for drawing.
            Graphics g = Graphics.FromImage(bitmap);
            g.SmoothingMode = SmoothingMode.AntiAlias;
            Rectangle rect = new Rectangle(0, 0, width, height);

            // Fill in the background.
            HatchBrush hatchBrush = new HatchBrush(HatchStyle.Wave, Color.LightGray, Color.White);
            g.FillRectangle(hatchBrush, rect);

            // Set up the text font.
            SizeF size;
            float fontSize = rect.Height + 1;
            Font font;
            StringFormat format = new StringFormat();
            format.Alignment = StringAlignment.Center;
            format.LineAlignment = StringAlignment.Center;

            // Adjust the font size until the text fits within the image.
            do
            {
                fontSize--;
                font = new Font(fontFamily, fontSize, FontStyle.Bold);
                size = g.MeasureString(text, font, new SizeF(width, height), format);
            } while (size.Width > rect.Width);

            // Create a path using the text and warp it randomly.
            GraphicsPath path = new GraphicsPath();
            path.AddString(text, font.FontFamily, (int)font.Style, font.Size, rect, format);
            float v = 4F;
            PointF[] points =
			{
				new PointF(random.Next(rect.Width) / v, random.Next(rect.Height) / v),
				new PointF(rect.Width - random.Next(rect.Width) / v, random.Next(rect.Height) / v),
				new PointF(random.Next(rect.Width) / v, rect.Height - random.Next(rect.Height) / v),
				new PointF(rect.Width - random.Next(rect.Width) / v, rect.Height - random.Next(rect.Height) / v)
			};
            Matrix matrix = new Matrix();
            matrix.Translate(0F, 0F);
            path.Warp(points, rect, matrix, WarpMode.Perspective, 0F);

            // Draw the text.
            hatchBrush = new HatchBrush(HatchStyle.DashedUpwardDiagonal, Color.DarkGray, Color.Black);
            g.FillPath(hatchBrush, path);

            // Add some random noise.
            int m = Math.Max(rect.Width, rect.Height);
            for (int i = 0; i < (int)(rect.Width * rect.Height / 30F); i++)
            {
                int x = random.Next(rect.Width);
                int y = random.Next(rect.Height);
                int w = random.Next(m / 50);
                int h = random.Next(m / 50);
                g.FillEllipse(hatchBrush, x, y, w, h);
            }

            // Clean up.
            font.Dispose();
            hatchBrush.Dispose();
            g.Dispose();

            Message message = new Message();
            message.CaptchaImage = bitmap;
            message.CaptchaHash = Convert.ToBase64String(MD5.Create().ComputeHash(Encoding.UTF8.GetBytes(text)));

            return message;
        }

        private string generateRandomString(int size)
        {
            StringBuilder builder = new StringBuilder();
            Random random = new Random(DateTime.Now.Millisecond);
            char ch;
            for (int i = 0; i < size; i++)
            {
                ch = Convert.ToChar(Convert.ToInt32(Math.Floor(26 * random.NextDouble() + 65)));
                builder.Append(ch);
            }
            return builder.ToString();
        }
    }
}
